Facet joint fusion devices and methods

ABSTRACT

A method for promoting fusion of and/or stabilizing a facet joint between two adjacent vertebrae comprises clamping the two adjacent vertebrae across the facet joint to apply a compressive force across the joint. Apparatus for promoting fusion of and/or stabilizing a facet joint comprises at least one cinchable tether and at least one locking member coupled with the tether for locking the cinched tether to maintain compressive force across the facet joint. The tether is adapted to extend through at least one hole through each of two adjacent vertebrae, across the facet joint.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 11/155,077(Attorney Docket No. 022307-000110US), filed on Jun. 16, 2005, whichclaimed the benefit of provisional application 60/581,196 (AttorneyDocket No. 022307-000100US), filed on Jun. 17, 2004, the fulldisclosures of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to medical devices, methods and systems.More specifically, the invention relates to devices, methods and systemsfor promoting fusion of and/or stabilizing a facet joint of a spine.

Approximately 80% of Americans experience at least a single episode ofsignificant back pain in their lifetime. For many people, back pain is achronic, often debilitating disorder. The direct costs of treating backpain, as well as the indirect costs, such as lost wages and decreasedproductivity, are staggering.

Although back pain may be caused by a number of different factors, manycases of back pain are caused by conditions related to the spinal (or“vertebral”) column. The vertebral column is made up of bones(vertebrae) and intervertebral discs that reside in the joint spacesbetween the vertebral bodies of the vertebrae. Three joints residebetween every two adjacent vertebrae—one larger intervertebral jointbetween the two intervertebral bodies and two facet joints locatedposterolaterally relative to the vertebral bodies. These three jointsshare the load applied between every set of two vertebrae. Many spinalailments are caused by degeneration, injury or deformity of thesevertebral joints and/or intervertebral discs.

Treatment of spinal pain typically begins with conservative,non-surgical methods, such as rest, heat, analgesics, physical therapyand manipulation. Unfortunately, however, conservative treatments failin a significant number of spinal pain patients, and surgery is oftenrequired. Current surgical procedures for treating intervertebral discand joint maladies include decompressive surgery, in which all or partof an intervertebral disc and/or the spinal laminae and facets areremoved, decompression with fusion of the joint (or “arthrodesis”), andarthrodesis alone. Intervertebral joint arthrodesis involves fusing twoadjacent vertebrae to stop the motion between those vertebrae.

Decompression (removal of structures compressing the spinal nervesincluding laminae, facet joints and/or intervertebral discs) is a verycommon surgical procedure that is very effective in promptly relievingsignificant pain derived from pressure on spinal nerve roots(“radicular” pain). The overall success rates for decompression alone,however, range from 48% to 89%. Spinal fusion is sometimes needed incombination with decompression to more successfully treat spinal pain.

Intervertebral fusion is designed to stop the motion at a painfulvertebral joint, which in turn should decrease pain generated from thejoint. It is also performed to stabilize an unstable intervertebralsegment, which if left unfused, could cause recurrent compression of thespinal nerves. Fusion procedures involve adding bone graft to an area ofthe spine to set up a biological response that causes the bone graft togrow between the two vertebral elements and thereby stop the motion atthat segment. Often, some type of support structure is attached to thetwo vertebrae being fused, to hold the vertebrae in a stable positionrelative to one another while the bone graft material causes fusion.Typical support structures, for example, include bone screws (or“pedicle screws”) attached to rods. Discectomy combined with fusion hasbeen the most common surgical treatment for symptomatic cervicalspondylosis for over 40 years. Good to excellent results have beenreported in 52-100% of anterior lumbar interbody fusions and 50-95% ofposterior lumbar interbody fusions.

A number of different spinal fusion surgical procedures are currently inuse. The most common fusion procedure performed in lumbar surgery isposterolateral intertransverse fusion. Although the technique is oftenquite successful, the standard procedure often causes significant traumato the paraspinous muscles. These muscles must be stripped from thetransverse processes and retracted for an extended period of time toexpose the underlying bone, which can result in denervation,devascularization, and ischemia of these important muscles, leading toatrophy and necrosis. Significant spasm in the short term and atrophyand necrosis in the long term contribute to the morbidity and sequelaeof fusion. The clinical effect of this muscle morbidity can besignificant postoperative pain and functional impairment in theconvalescent period, as well as permanent impairment of paraspinallumbar muscular function.

Other surgical techniques for performing spinal fusion are associatedwith similar and/or additional risk factors. For example, posteriorlumbar interbody fusion (“PLIF”) achieves fusion by inserting bonegrafts, titanium threaded cages, bone dowels, or carbon fiber spacersfilled with bone graft into an intervertebral disc space. All PLIFtechniques require removal of the posterior bone of the spinal canal(laminectomy), retraction of the nerves and removal of the disc materialfrom within the disc space, any of which may cause complications.Another procedure, anterior lumbar interbody fusion (“ALIF”), is similarto PLIF, except that in ALIF the disc space is fused by approaching thespine through the abdomen instead of through the back. An additional,and potentially significant, risk of ALIF is potential damage toabdominal structures, such as the large arteries that supply blood tothe legs.

As mentioned above, with many spinal fusion procedures, some type ofsupport structure, such as screws, rods, pins, cages and/or the like, isused to hold the adjacent vertebrae in place while they are fusingtogether with the help of the bone graft, bone adhesive, or the like.One of the primary risks of fusion surgery is that a solid fusion willnot be obtained (“nonunion”), thus requiring further surgery. One of themain challenges of intervertebral fusion surgery is to stabilize thevertebrae long enough, using the support structure(s), so that they havetime to fuse. Another challenge is actually applying the supportstructure properly. Pedicle screws, for example, may often be effectiveat providing support during intervertebral fusion, but they can bedifficult to place properly, and if misplaced may cause nerve rootand/or vascular injury.

As the population continues to age, surgical procedures for fusingand/or stabilizing vertebrae will become ever more common. Therefore, aneed exists for improved techniques, devices and systems for performingsuch procedures. Such improved methods and devices should ideallyfacilitate and/or enhance intervertebral fusion, while preventing orreducing the prevalence of complications or sequelae. Ideally, minimallyinvasive procedures would be developed that would provide stabilizationof an intervertebral joint for a sufficient period of time to allow thevertebrae to fuse. Also ideally, such procedures would be relativelysimple to use. At least some of these objectives will be met by thepresent invention.

BRIEF SUMMARY OF THE INVENTION

Methods, devices and systems of the present invention promote fusion ofand/or stabilize an intervertebral facet joint. Methods generallyinvolve clamping two vertebrae across a facet joint to apply compressiveforce to the joint. Devices include one or more cinchable tethers, whichin various embodiments may be passed through a hole extending throughtwo vertebrae and/or may circumscribe the two vertebrae. Someembodiments also include one or more bone surface contacting members,such as plates, washers or the like, which enhance the ability of thecinchable tether to apply compressive force. One advantage of variousembodiments of the invention is that they may be used to promote fusionand/or stabilization of one or more facet joints using a minimallyinvasive or less invasive procedure. In various embodiments, eitherpercutaneous or open surgical approaches may be used. In a number ofembodiments, techniques and devices of the invention may be used withother currently available devices or systems.

In one aspect of the present invention, a method for promoting fusion ofa facet joint between two adjacent vertebrae involves clamping the twoadjacent vertebrae across the facet joint to apply a compressive forceacross the joint. In some embodiments, the method further involvesforming at least one hole through the two vertebrae across the facetjoint. In such embodiments, clamping involves advancing a tether throughthe hole across the joint. Clamping may further involve cinching thetether to apply the compressive force, though cinching is not requiredin all embodiments.

In some embodiments, the hole extends through a first of the twovertebrae along a first axis and through a second of the two vertebraealong a second axis, so that advancing the tether through the holecauses the vertebrae to translate relative to each other. This“offset-hole” technique allows a surgeon to realign the vertebrae whilealso promoting fusion of and/or stabilizing the joint. In someembodiments, two holes are formed through the two vertebrae across thefacet joint, and a separate tether is advanced through each of the twoholes. Alternatively, two holes may be formed through the two vertebraeacross the joint, and one tether may be advanced through both holes. Invarious other embodiments, any other suitable combination of holes andtether(s) may be used.

Optionally, a first bone surface contacting member slidably coupled withthe tether may be contacted with a first of the two vertebrae, beforethe cinching step. The method may further comprise contacting a secondbone surface contacting member slidably coupled with the tether with asecond of the two vertebrae, also before the cinching step. One or morebone contacting members, such as plates, washers or the like, may helpdistribute force applied by the cinchable tether to more effectivelyapply compressive force across the joint.

The method may further include locking the cinched tether to maintainthe compressive force across the facet joint. In some embodiments, twoends of the cinched tether overlap, and locking the cinched tethercomprises locking the two ends together. For example, locking the twoends together may involve crimping at least one crimping member coupledwith the two ends. In another embodiment, locking the two ends togetherinvolves locking two locking members together, each locking member beingcoupled with one of the two ends of the tether. In some embodiments,cinching and locking the tether(s) may be performed with the same tool,while in other embodiments separate tools may be used.

In some embodiments, rather than forming a hole through the vertebrae,clamping may involve circumscribing the joint with a tether disposedover the vertebrae. In some cases, such a tether may be cinchable forapplying the compressive force. Optionally, the method may furtherinclude contouring external surfaces of the vertebrae to enhanceengagement of the tether with the surfaces.

In yet another embodiment, clamping comprises engaging a clamping devicewith external surfaces of the vertebrae across the joint. Alternatively,clamping may comprise releasing a shape-memory or spring-loaded clampingdevice from constraint to clamp the vertebrae and apply the compressiveforce.

The method may optionally further include preparing at least oneopposing surface of the two vertebrae, within the facet joint, byremoving cartilage from the surface. Another optional step may includeinserting at least one material into the facet joint to promote jointfusion. Such material(s) may include, for example, autologous bone, boneallograft, bone adhesive, bone morphogenic protein and/or bone growthpromoting materials. In various embodiments, any of the above methodsteps may be performed percutaneously or as part of an open surgicalprocedure. The fusion promoter may optionally be placed in a reservoiror depot to provide controlled release over time and/or infusion of newbone growth into a matrix. The reservoir is appropriately shaped to fitthe prepared surface. The reservoir might be made from knownbioresorbable implantable materials, such as collagen, gelfoam, andcopolymers of poly lactic and poly glycolic acid. Preparing the surfacemight involve removing cartilage and some of the bone at the surface toattain an appropriate geometry that fits the reservoir.

In another aspect of the present invention, a method for applying forceacross a facet joint between two vertebrae involves forming at least afirst hole through the two vertebrae across the facet joint, advancing afirst tether through the first hole across the joint, and cinching thetether. As with the above method, this technique may optionally furtherinclude contacting one or more bone surface contacting members slidablycoupled with the tether with one or both of the two vertebrae. In oneembodiment, two washers slidably disposed over the tether are contactedwith surfaces of the two vertebrae outside the facet joint. The methodmay also include locking the cinched tether to maintain the force acrossthe facet joint. Any of the features described above may be applied tothis method, according to various embodiments.

In another aspect of the invention, a method for stabilizing a facetjoint between two adjacent vertebrae comprises clamping the two adjacentvertebrae across the facet joint to apply a compressive force across thejoint. Another alternative to stabilize the joint is to place anelastomer insert into a prepared surface (after removal of cartilage andsome bone) and subsequently apply force to the joint to “sandwich” theelastomer insert. The insert is made from known implantable elastomerssuch as polyurethane or silicone. The elastomer insert allows somemotion at the joint. Again, any of the features described above may beapplied to this method.

In another aspect of the present invention, apparatus for promotingfusion of a facet joint between two adjacent vertebrae comprises atleast one cinchable tether adapted to extend through at least one holethrough each of two adjacent vertebrae across the facet joint and atleast one locking member coupled with the tether for locking the cinchedtether to maintain compressive force across the facet joint. Someembodiments further include at least a first bone surface contactingmember slidably coupled with the tether for contacting a first of thetwo vertebrae external to the facet joint. The apparatus may furtherinclude a second bone surface contacting member coupled with the tetherfor contacting a second of the two vertebrae external to the facetjoint. In such embodiments, cinching the tether applies compressiveforce between the first and second bone surface contacting membersacross the facet joint.

In some embodiments, each of the first and second bone surfacecontacting members comprises a plate having at least one hole allowingfor passage of the tether. Some embodiments include two cinchabletethers, and each plate includes two holes allowing for passage of thetwo tethers. Optionally, the plates may be curved to conform to surfacesof the two vertebrae. In some embodiments, the plates are malleable toconform to surfaces of the two vertebrae. Alternatively, the plates maybe completely rigid, or each plate may include a rigid portion and amalleable portion for contacting a surface of one of the vertebrae. Anysuitable materials may be used to manufacture the plates, such as butnot limited to titanium, titanium alloys, stainless steel,cobalt-chromium alloy, carbon filled PEEK, ultra-high molecular weightpolyethylene, silicone, polyurethane, SEBS-based materials and/or thelike. (SEBS-based materials are a family of thermoplastic syntheticrubber materials, with SEBS standing forstyrene-ethylene-butadiene-styrene). In some embodiments, the apparatusmay be made predominantly of radiolucent materials, with one or moreradiopaque markers facilitating visualization of the device. In otherembodiments, the apparatus (or one or more parts of the apparatus) maybe made of radiopaque materials.

Some embodiments include a curved bone contacting member adapted to wraparound surfaces of the two vertebrae adjacent the facet joint. In theseembodiments, cinching the tether compresses the curved bone contactingmember to apply compressive force across the facet joint. Optionally, atleast part of the bone contacting member may be malleable to conform tothe surfaces of the two vertebrae.

The tether (or tethers) may have any suitable length, diameter,configuration or the like, and may be made of any suitable material orcombination of materials. In some embodiments, for example, the tethermay comprise a cord, cable, suture, wire, T-tag or the like. Materialsused to form a tether may include, but are not limited to, stainlesssteel, cobalt-chromium alloy, titanium, Nitinol, ultra-high molectularweight polyethylene, cobalt-chromium alloy, PTFE, PET and/or the like.

Similarly, the locking member (or multiple locking members) may have anysuitable size, shape and configuration and may be made of any suitablematerial(s). In one embodiment, the locking member comprises at leastone crimping member coupled at or near both ends of the tether andslidable along at least one end of the tether. In another embodiment,the locking member comprises a T-tag. In yet another embodiment, thelocking member comprises at least a first locking member coupled withthe tether at or near a first end of the tether and at least a secondlocking member coupled with tether at or near a second end of thetether, wherein the first and second locking members lock together. Inanother embodiment, locking member comprises a lasso member coupled withone end of the tether and a rivet slidably coupled with the tether andadapted to engage and lock with the lasso.

In another aspect of the present invention, a clamping device forstabilizing a facet joint between two adjacent vertebrae includes atleast one bone surface contacting member for engaging at least one ofthe two vertebrae and at least one cinchable tether slidably coupledwith the bone surface contacting member and passable through a holeextending through each of the two vertebrae, across the facet joint. Thecinchable tether and the bone surface contacting member are adapted toapply compressive force across the facet joint. In various embodiments,this apparatus may have any of the features described above.

In yet another aspect of the present invention, a system for promotingfusion of a facet joint between two adjacent vertebrae includes a facetjoint clamping device and a drill for forming the at least one holethrough the two vertebrae. The facet joint clamping device includes atleast one cinchable tether adapted to extend through at least one holethrough each of two adjacent vertebrae, across the facet joint.Optionally, the clamping device may further include any of the devicefeatures described above.

In some embodiments, the clamping device, the drill or both arecalibrated to form the at least one hole through the vertebrae so as torealign the two vertebrae when the cinchable tether is passedtherethrough. The system may optionally further include an access devicefor providing access to the two vertebrae. In various embodiments, theaccess device may provide for percutaneous access or open surgicalaccess to the two vertebrae.

The system may also include one or more bone preparation devices forpreparing one or more bone surfaces within the joint by removing atleast one of cartilage or bone. In one embodiment, for example, a bonepreparation device comprises a flexible cutting guide and a cuttingdevice passable over the cutting guide, with the guide and the cuttingdevice adapted to remove cartilage from the bone surfaces whileminimizing removal of bone. In some embodiments, the system furtherincludes at least one fusion promoting material adapted for insertioninto the joint to promote fusion of the joint.

These and other aspects and embodiments of the invention are describedfurther below with reference to the drawing figures.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIG. 1 is a posterior perspective view of a lumbar portion of avertebral column, with fusion/stabilization devices attached across twofacet joints according to one embodiment of the present invention;

FIG. 2 is a superior view of a lumbar vertebra and part of an adjacentvertebra, with the fusion/stabilization device of FIG. 1 attached acrossthe facet joints;

FIG. 3 is a lateral view of two adjacent vertebrae, with thefusion/stabilization device of FIG. 1 attached across the facet joints;

FIG. 4 is a perspective view of a clamping device including a tether andlocking member, according to one embodiment of the present invention;

FIGS. 4A and 4B are perspective and end-on views, respectively, of thelocking member of FIG. 4;

FIG. 5 is a perspective view of a clamping device including a tether andlocking members according to another embodiment of the presentinvention;

FIG. 6 is a perspective view of two bone surface contacting membersaccording to one embodiment of the present invention;

FIG. 6A are end-on views of three sizes of bone surface contactingmembers according to three different embodiments of the presentinvention;

FIG. 7 is a perspective view of a portion of a tether extending throughapertures on two bone surface contacting members according to oneembodiment of the invention;

FIG. 8 is a superior view of a lumbar vertebra and part of an adjacentvertebra, with a fusion/stabilization device applied to two facet jointsaccording to another embodiment of the invention; and

FIG. 9 is a superior view of a lumbar vertebra and part of an adjacentvertebra, with a fusion/stabilization device applied to two facet jointsaccording to another embodiment of the invention.

FIG. 10 illustrates an elastomeric insert for facet joint fusion.

FIGS. 11A-11E illustrate alternative embodiments of elastomeric insertsand reservoirs for facet joint fusion.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a posterior perspective view of the most inferior four lumbarvertebrae (L2-L5) and a portion of the sacrum S. Attached across the twofacet joints F between the L4 and L5 vertebrae is a clamping device 10according to one embodiment of the present invention. Each clampingdevice 10 includes a tether 12 and two bone surface contacting members14 (only one contacting member 14 is visible for each device 10 in FIG.1.) As is described in further detail below, two holes are drilledthrough each of the facet joints F of L4 and L5, tethers 12, coupledwith bone contacting members 14, are passed through the holes, andtethers 12 are cinched to apply compressive force across the facetjoints F, thus promoting fusion of and/or stabilizing the joints F.

FIGS. 2 and 3 provide superior and lateral views, respectively, ofclamping device 10 from FIG. 1. In FIG. 2, it can be seen that tethers12 extend through holes (dotted lines) in the vertebrae L4, L5 andacross the facet joints F. Typically, the holes are drilled or otherwiseformed through the superior articular process SAP of the inferiorvertebrae (in this case L5) and through the inferior articular processIAP of the superior vertebrae (in this case L4). Of course, clampingdevice 10 may be applied across one or more facet joints of any twovertebrae, and its use is in no way limited to lumbar vertebrae or anyother vertebrae. Additionally, if holes are formed to apply clampingdevice 10, they may be formed through any suitable part of adjacentvertebrae in order to cross the facet joints F, and in variousembodiments such holes may pass through only one articular process, orthrough neither articular process.

Once tether 12 is passed through one or more holes in two vertebrae L4,L5 and bone surface contacting members 14 are engaged with vertebralbone, tether 12 is typically cinched, to apply compressive force againstthe facet joint F, and locked, to maintain the force. Thus, clampingdevice 10 may suitably include one or more locking members 16 forlocking the cinched tether 12. Locking member 16 may comprise anysuitable device for maintaining the force of cinched tether, as will bedescribed in further detail below.

In various embodiments, each bone surface contacting member 14 mayinclude one aperture or hole for passage of tether 12, two holes, ormore than two holes. Furthermore, clamping device 10 may include onetether 12 or multiple tethers 12, in various embodiments. In theembodiment shown in FIGS. 1-3, one tether 12 extends through both holeson the two bone surface contacting members 14 of each device 10.

Referring now to FIG. 4, one embodiment of a tether 12, slidably coupledwith a locking member 16, is shown. Locking member 16 is shown ingreater detail in FIGS. 4A and 4B. In various embodiments, tether 12 maybe made of any of a number of suitable materials, such as but notlimited to stainless steel, cobalt-chromium alloy, titanium, Nitinol,ultra-high molectular weight polyethylene, cobalt-chromium alloy, PTFEor PET. Locking member 16 may similarly be made of any suitablematerial. In one embodiment, locking member 16 made of a material thatallows it to be crimped to lock the two ends of tether 12. In variousembodiments, locking member 16 may be fixedly attached to one end oftether and slidable over the other end, or may be slidable over bothends of the tether. Generally, locking member may have any suitableshape, size or configuration, according to various embodiments.

For example, and with reference now to FIG. 5, in one embodiment atether 22 is coupled at one end with a lasso-like circular lockingmember 24, and a rivet 26 is slidably disposed over the other end oftether 22. Rivet 26 may be advanced over tether 22 into the opening ofcircular member 24, and circular member 24 may then be crimped down tolock over rivet 26. Alternatively, rivet 26 may be sized to lock withincircular member 24 without crimping. In various embodiments, any othersuitable locking member(s) may be included, such as T-tags, snap-fitlocking members, pressure-fit members or the like.

Referring now to FIG. 6, bone surface contacting members 14 may have anysuitable shape, size and configuration and may be made of any suitablematerial or combination of materials. In some embodiments, contactingmembers 14 are completely rigid, while in other embodiments they may bepartly or completely malleable. As illustrated in FIG. 6, someembodiments include a rigid outer layer 17 or shell coupled with amalleable inner layer 15 for contacting bony surfaces of vertebrae.Examples of materials from which bone surface contacting members 14 maybe constructed include, but are not limited to, titanium, titaniumalloys, stainless steel, cobalt-chromium alloy, carbon filled PEEK,ultra-high molectular weight polyethylene, silicone, polyurethane andSEBS-based materials. Contacting members 14 may have two apertures 19for slidably passing along tether 12, or may have one aperture 19 or anyother suitable number.

As illustrated in FIG. 6A, in various embodiments bone surfacecontacting members 14A-14C may have any of a number of suitable sizesand shapes. In one embodiment, a number of differently shaped contactingmembers 14A-14C may be provided in a kit, so that members 14A-14C may beselected based on the size and shape of the vertebrae on which they areto be placed. In alternative embodiments, contacting members 14 may beformed as washers, plates or the like, and may be flat or curved. In oneembodiment, a single curved plate is used, rather than two contactingmembers 14, the curved plate adapted to wrap around two vertebraeadjacent the facet joint.

FIG. 7 shows tether 12 extending through two bone surface contactingmembers 14. Again, in various embodiments, multiple tethers 12 may beused, one, two or any suitable number of contacting members 14 may beused, and/or the like.

In an exemplary method for using clamping device 10 to promote facetjoint fusion and/or stabilization, a first step involves gaining accessto the facet joint(s) to be fused/stabilized. Access may be gained viaany suitable technique and route, using any suitable devices or systems.For example, some suitable access methods will be minimally invasive andpercutaneous, while others may involve open surgical approaches. In someembodiments, currently available minimally invasive access systems, suchas the MAST™ system provided by Medtronic, Inc. or the ATAVI™ systemprovided by Endius, Inc. may be used.

Once access is gained, some embodiments involve preparing the surfacesof the facet joint by removing cartilage. In alternative embodiments,currently available devices, such as curettes, may be used for suchpreparation, or specialized facet joint preparation devices, such as aflexible cutting guide and a cutter, may be used. One or more holes maythen be formed through adjacent vertebrae across the facet joint(s).Holes may be formed using currently available drilling devices, such asthe CurveTek™ bone tunneling system provided by Arthrotek, Inc., oralternatively by any other suitable device(s). In some instances, a holemay be formed so that it is offset through one vertebra relative to theadjacent vertebra. When tether 12 is then extended through the offsetholes and cinched, the facets translate relative to one another, thusrealigning the joint. Thus, in some embodiments, realignment as well asfusion/stabilization may be achieved. Some embodiments include jigs,calibrations and/or the like to facilitate offsetting of holes betweenvertebrae.

Once the holes are formed in two adjacent vertebrae, one or more tethers12 are passed through the holes. One or more bone surface contactingmembers 14 may be passed along each tether 12 to contact the vertebrae.Tether 12 is then cinched and locked with one or more locking members 16to apply and maintain compressive force across the joint.

If joint fusion is desired, at any suitable point in the process one ormore joint fusion materials may be placed in the joint, between the twoarticular surfaces. Such materials may include, for example, autologousbone, bone allograft, bone adhesive, bone morphogenic proteins and/orbone growth promoting material(s).

Referring now to FIG. 8, in an alternative embodiment of the invention,no holes are placed through the vertebrae. Instead, one or more tethers32 are wrapped or circumscribed around the vertebrae adjacent the facetjoint F and then cinched to apply compressive force across the joint.Tethers 32 may be coupled with one or more locking members 36 to retainforce across the joint F. In various embodiments, bone surfacecontacting members may or may not be used. Some embodiments furtherinclude preparing external surfaces of the vertebrae to enhanceengagement of tether(s) 12 with the vertebrae, for example by formingone or more troughs 38 or paths for holding tether(s) 12.

Referring to FIG. 9, another embodiment may involve releasing ashape-memory or spring-loaded clamping device 42 from constraint toengage the vertebrae adjacent a facet joint F and to apply compressiveforce across the joint. Clamping device 42 may be made of any suitableshape-memory material, such as Nitinol, or may be spring loaded in adelivery device.

FIG. 10 shows a superior view of the facets with inserts 100 at thejoints which are held together by tethers 10 and washers. The insert maycomprise a reservoir 106 which optionally includes or provides anelastomeric insert. FIGS. 11A-11E show two embodiments of thereservoir/elastomer insert. The first embodiment shows an insert 110with a central hole 112 to pass a tether through. The number of holesdepends on the number of tethers. If the insert is a reservoir then itwould be made of a bioresorbable material. The insert 110 is made froman elastomer in instances where the joint is being stabilized but notfused. The second embodiment 120 (FIGS. 11D and 11E) includes a channel122 on both surfaces of the insert that face the bone. The channel 122serves as a reservoir for fusion enhancing substances as an alternativeto sponge-like bioresorbable matrices.

Although the foregoing is a complete and accurate description of thepresent invention, a number of various additions, changes or the likemay be made to various embodiments described above without departingfrom the scope of the invention. Therefore, the description above isprovided primarily for exemplary purposes and should not be interpretedto limit the scope of the invention as it is set forth in the claims.

1. Apparatus for promoting fusion of a facet joint between two adjacentvertebrae, the apparatus comprising: at least one cinchable tetheradapted to extend through at least one hole through each of two adjacentvertebrae, across the facet joint; a first bone surface contactingmember slidably coupled with the tether for contacting a first of thetwo vertebrae external to the facet joint; a second bone surfacecontacting member coupled with the tether for contacting a second of thetwo vertebrae external to the facet joint, wherein cinching the tetherapplies compressive force between the first and second bone surfacecontacting members across the facet joint; and at least one lockingmember coupled with the tether for locking the cinched tether tomaintain compressive force across the facet joint.
 2. Apparatus as inclaim 1, wherein each of the first and second bone surface contactingmembers each comprise a plate having at least one hole allowing forpassage of the tether.
 3. Apparatus as in claim 1, further comprising asecond cinchable tether, wherein each plate comprises two holes allowingfor passage of the two tethers.
 4. Apparatus as in claim 3, wherein theplates are curved to conform to surfaces of the two vertebrae. 5.Apparatus as in claim 3, wherein the plates are malleable to conform tosurfaces of the two vertebrae.
 6. Apparatus as in claim 3, wherein eachof the plates comprises: a rigid portion; and a malleable portion forcontacting a surface of one of the vertebrae.
 7. Apparatus as in claim3, wherein the plates comprise at least one material selected from thegroup consisting of titanium, titanium alloys, stainless steel,cobalt-chromium alloy, carbon filled PEEK, ultra-high molecular weightpolyethylene, silicone, polyurethane and SEBS-based materials. 8.Apparatus as in claim 1, wherein the apparatus comprises primarilyradiolucent materials or including at least one radiopaque marker. 9.Apparatus as in claim 1, further comprising a curved bone contactingmember adapted to wrap around surfaces of the two vertebrae adjacent thefacet joint, wherein cinching the tether compresses the curved bonecontacting member to apply compressive force across the facet joint. 10.Apparatus as in claim 1, wherein the tether is selected from the groupconsisting of a cord, a cable, a suture, a wire and a T-tag. 11.Apparatus as in claim 10, wherein the tether comprises at least onematerial selected from the group consisting of stainless steel,titanium, Nitinol, ultra-high molecular weight polyethylene,cobalt-chromium alloy, PTFE, and PET.
 12. Apparatus as in claim 1,wherein the at least one locking member comprises at least one crimpingmember coupled at or near both ends of the tether and slidable along atleast one end of the tether.
 13. Apparatus as in claim 1, wherein the atleast one locking member comprises: at least a first locking membercoupled with the tether at or near a first end of the tether; and atleast a second locking member coupled with tether at or near a secondend of the tether, wherein the first and second locking members locktogether.
 14. Apparatus as in claim 1, wherein the at least one lockingmember comprises: a lasso member coupled with one end of the tether; anda rivet slidably coupled with the tether and adapted to engage and lockwith the lasso.
 15. A system for promoting fusion of a facet jointbetween two adjacent vertebrae, the system comprising: a facet jointclamping device comprising at least one cinchable tether adapted toextend through at least one hole through each of two adjacent vertebrae,across the facet joint; and a drill for forming the at least one holethrough the two vertebrae.
 16. A system as in claim 15, furthercomprising at least one locking member coupled with the tether forlocking the cinched tether to maintain compressive force across thefacet joint.
 17. A system as in claim 15, further comprising at leastone cinching tool for applying force to the cinchable tether.
 18. Asystem as in claim 15, wherein the cinching tool is adapted to apply atleast one locking member to the cinchable tether to maintain the forceapplied to the tether.
 19. A system as in claim 15, wherein at least oneof the clamping device and the drill are calibrated to form the at leastone hole through the vertebrae so as to realign the two vertebrae whenthe cinchable tether is passed therethrough.
 20. A system as in claim15, further comprising an access device for providing access to the twovertebrae.
 21. A system as in claim 20, wherein the access deviceprovides for percutaneous access to the two vertebrae.
 22. A system asin claim 20, wherein the access device provides for open surgical accessto the two vertebrae.
 23. A system as in claim 15, further comprising atleast one bone preparation device for preparing one or more bonesurfaces within the joint by removing at least one of cartilage or bone.24. A system as in claim 23, wherein the bone preparation devicecomprises: a flexible cutting guide; and a cutting device passable overthe cutting guide, wherein the guide and the cutting device are adaptedto remove cartilage from the bone surfaces while minimizing removal ofbone.
 25. A system as in claim 15, further comprising at least onefusion promoting material adapted for insertion into the joint topromote fusion of the joint.
 26. A system as in claim 15, wherein theclamping device further comprises at least a first bone surfacecontacting member slidably coupled with the tether for contacting afirst of the two vertebrae external to the facet joint.
 27. A system asin claim 26, wherein the clamping device further comprises a second bonesurface contacting member coupled with the tether for contacting asecond of the two vertebrae external to the facet joint, whereincinching the tether applies compressive force between the first andsecond bone surface contacting members across the facet joint.
 28. Asystem as in claim 27, wherein each of the first and second bone surfacecontacting members comprises a plate having at least one hole allowingfor passage of the tether.
 29. A system as in claim 15, wherein theclamping device further comprises a curved bone contacting memberadapted to wrap around surfaces of the two vertebrae adjacent the facetjoint, wherein cinching the tether compresses the curved bone contactingmember to apply compressive force across the facet joint.
 30. A systemas in claim 15, wherein the tether is selected from the group consistingof a cord, a cable, a suture, a wire and a T-tag.
 31. A system as inclaim 15, wherein the tether comprises at least one material selectedfrom the group consisting of stainless steel, cobalt-chromium alloy,titanium, Nitinol, ultra-high molectular weight polyethylene,cobalt-chromium alloy, PTFE, and PET.
 32. A system as in claim 15,wherein the at least one locking member comprises at least one crimpingmember coupled at or near both ends of the tether and slidable along atleast one end of the tether.
 33. A system as in claim 15, wherein the atleast one locking member comprises a T-tag locking member.
 34. A systemas in claim 15, wherein the at least one locking member comprises: atleast a first locking member coupled with the tether at or near a firstend of the tether; and at least a second locking member coupled withtether at or near a second end of the tether, wherein the first andsecond locking members lock together.
 35. A system as in claim 15,wherein the at least one locking member comprises: a lasso membercoupled with one end of the tether; and a rivet slidably coupled withthe tether and adapted to engage and lock with the lasso.